qmk_firmware/FAQ.md

# Build
## 'make clean' needs after changing config.h
To build with new **config.h** you need

    $ make clean

## WINAVR is obsolete
It is no longer recommended and may cause some problem.
See [Issue #99](https://github.com/tmk/tmk_keyboard/issues/99).

## USB stack: LUFA or PJRC?
Use **LUFA**.

**PJRC** stack won't be supported actively anymore. There is no reason to hesitate to use LUFA except for binary size(about 1KB lager?). See also [Issue #50](https://github.com/tmk/tmk_keyboard/issues/50) and [Issue #58](https://github.com/tmk/tmk_keyboard/issues/58).

But **PJRC** is still very useful for debug and development purpose.

# Degug Console
## hid_listen can't find device
When debug console of your device is not ready you will see like this:

    Waiting for device:.........

once the device is pluged in then *hid_listen* finds it you will get this message:

    Waiting for new device:.........................
    Listening:

Check if you can't get this 'Listening:' message:
- build with `CONSOLE_ENABLE=yes` in **Makefile**.

## Can't get message from console
Check:
- connect the device to *hid_listen*. See above.
- push **LShift+RShift+d** to enable debug. See [Magic Commands](https://github.com/tmk/tmk_keyboard#magic-commands).
- set `debug_enable=yes` usually in `matrix_init()` in **matrix.c**.
- try using 'print' function instead of debug print. See **common/print.h**.
- disconnect other devices with console function. See [Issue #97](https://github.com/tmk/tmk_keyboard/issues/97).

***

# Miscellaneous
## NKRO Doesn't work
Build with this option of Makefile

    NKRO_ENABLE = yes

And use `Magic` command **N** to toggle NKRO feature.
At this time NKRO is not used by default even if it is build with `NKRO_ENABLE`, you still need the `Magic`.

To turn on NKRO by default see this fix.
https://github.com/shayneholmes/tmk_keyboard/commit/b8375a0
```
--- a/common/host.c
+++ b/common/host.c
@@ -24,7 +24,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
 #ifdef NKRO_ENABLE
-bool keyboard_nkro = false;
+bool keyboard_nkro = true;
 #endif
 
 static host_driver_t *driver;
```

## TrackPoint needs reset circuit(PS/2 mouse support)
Without reset circuit you will have inconsistent reuslt due to improper initialize of the hardware. See circuit schematic of TPM754.

- http://geekhack.org/index.php?topic=50176.msg1127447#msg1127447
- http://www.mikrocontroller.net/attachment/52583/tpm754.pdf


## Can't read comlumn of matrix beyond 16 
Use `1UL<<16` intead of `1<<16` in `read_cols()` in **matrix.h** when your columns goes beyond 16.

In C `1` means one of **int** type which is **16bit** in case of AVR so you can't shift left more than 15. You will get unexpected zero when you say `1<<16`. You have to use **unsigned long** type with `1UL`.

http://deskthority.net/workshop-f7/rebuilding-and-redesigning-a-classic-thinkpad-keyboard-t6181-60.html#p146279